1. Field of the Invention
The present invention relates to girder systems for bridges, and particularly to a roll beam bridge. It includes a method of forming compression splices for steel beams, a system of girders for the frame of the bridge using rolled beams, and a bed of reinforced concrete planks.
2. Description of the Related Art
Bridges may be broadly classified as fixed or moveable. Fixed bridges may be further classified as beam, arch and suspension. While all bridges must carry the full weight of the bridge and the traffic on their foundation, it is significant to note that arch bridges are in compression and thrust outward on their end supports or bearings, while suspension bridges are in tension and apply a continual pull on their end supports.
While there are several types of fixed, beam bridges, for purposes of understanding the present invention in terms of the related art, it is useful to note that beam bridges include types known as rolled beam, plate girder, box girder and continuous. Rolled beam bridges use steel girders rolled as a single, integral unit at the mill in various shapes, such as I-beam, H-beam, T-beam, etc. Roll beam bridges generally are useful for short spans of 50 to 150 feet. Plate girder bridges employ steel girders joined to make different shapes by welding or by bolts or rivets. An I-beam, for example, may be constructed from three plates, a top flange, bottom flange, and web, often using angles to construct the girder. Plate girders generally are capable of having greater stiffness than rolled beams and permit longer spans. Box girders are constructed from four plates welded together into a box shape, and have been used for spans from 100 ft to 850 ft. Continuous bridges are supported at three or more points, and are capable of resisting bending moments and shear at all sections throughout their length.
An additional consideration includes the material used to construct the beams. Modern bridges are generally constructed from steel or concrete. Bridges made of reinforced concrete were either arch bridges, slab bridges of quite short span, generally consisting of a reinforced concrete slab extending from end support to end support, or deck girder bridges having a concrete slab integral with concrete girders. The development of prestressed concrete has led to increased use of concrete in bridge construction. Prestressing involves stretching the steel reinforcement bars or wires before or during casting of the concrete to increase the compressive strength of the concrete, saving about one-fourth the volume of concrete and about three-fourths the weight of reinforcing steel. Prestressed concrete can be used in spans up to 600 feet, and longer spans are possible with cable support.
The present invention relates to a single span rolled beam bridge of about 60 feet to 150 feet in length using steel girders of the rolled beam variety. Currently rolled beam girders are custom made, in lengths of 120 feet or more. Such construction methods require special permits for transportation of the beams to the bridge site. Once erected, contractors must lay out concrete forms between the beams, which requires that the workers be supported by cables, construction of sufficient foundations for safety equipment, and other safety measures which alone add about 90 days to construction time, as well as hazards to health and safety. The present invention allows prefabricated construction of the beams from roll beam girders in sections which may be transported to the job site without special permits, and flooring made from precast reinforce concrete planks. A novel method of making a compression splice between the steel girders permits such a construction technique. The construction of the sections and the splice permit the moments to be fixed and borne by the end supports. The prior art does not disclose a similar method of bridge or girder construction.
U.S. Pat. No. 811,257, issued Jan. 30, 1906 to Joseph B. Strauss, discloses a concrete or concrete and steel bridge having hollow concrete forms for beam girders and hollow concrete forms for transverse joists, connected by steel bars and loops, the hollow forms being erected to form a frame and filled with concrete to form a concrete bridge using prefabricated forms. U.S. Pat. No. 1,688,128, issued Oct. 16, 1928 to Ernest Moccetti, discloses reinforced concrete girders having webbed structures in which the concrete in not continuously reinforced, but has main tensile reinforcements in zones of the greatest tension and special tension reinforcements in the webs for lighter weight, greater internal strength and smaller bulk.
U.S. Pat. No. 2,336,622, issued Dec. 14, 1943 to Robert G. LeTourneau, teaches the use of trapezoidal box beam girders with joists extending into a supported by the beams, supporting a solid metal flooring. U.S. Pat. No. 3,365,852, issued Jan. 30, 1968 to Ronald J. Pitillo, shows structural framing units made by cutting a triangular piece from the web of an I-beam, cutting the I-beam longitudinally with cutting torches, and rejoining the beam in the shape of trusses, etc., using the triangle to support the joints. Pitillo shows the construction of specialty trusses and roof beams, but no method suitable to the construction of bridge beams, and particular not to end sections and keystone sections having multiple beams cut in specific ratios of web beam sizes and at specific angles and joined by bolts through the flanges to form a splice.
U.S. Pat. No. 3,425,076, issued Feb. 4, 1969 to Ulrich Finsterwalder, shows a method for joining the spans of a highway bridge between two cantilevered spans using resilient tensioning members rigidly connected to adjoining sections composed of tendons piercing concrete joists and covered by the road surface. U.S. Pat. No. 4,042,991, issued Aug. 23, 1977 to Macy, et al., describes a portable load carrying structure, particularly for use in the Arctic to span breaks in the ice, consisting of I-beams, preferably made of aluminum, hinged together in parallel so they fold for compact storage and transport.
U.S. Pat. No. 5,526,544, issued Jun. 18, 1996 to Wiedeck, et al., shows a bridge having a flat base body and at least one roadway surface pivotally connected to the base body where the roadway surface may be pivoted above the base body to form a bridge. German Patent No. 1,939,737, published Feb. 18, 1971, teaches a method of building a prestressed concrete bridge which uses an orthotropic concrete slab roadway.
Soviet Invention Certificate No. 1,474,201, published Apr. 23, 1989, describes a method of building a bridge with a "zero bending moment" using alternating sections composed of two parts, including two end span sections with beams having a reinforced concrete top and metal bottom, and a center section with a metal top and reinforced concrete bottom with an orthotropic roadway in which the metal parts of the beams are placed under tension by tension members at the end supports and the junctions of the end sections with the center section, and in which the concrete is in compression. The bride is a continuous bridge.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a roll beam girder system for bridges solving the aforementioned problems is desired.